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451 Heater Controller Fix

Mod Details
PremiumYes Difficulty Mod ID1639 CreditShaun L For451 ED451 Fortwo Link Copy to Clipboard

If you are having heater or climate controls issues as mentioned here, site viewer Shaun L reckons he’s found the issue. If he’s correct, it’s a fairly easy fix. This is the potentiometer (pot) that moves with the temperature selector inside the heater controller. Opening the controller can be seen here.

It’s made by Piher and despite saying 10K on it, that’s not the resistance. That means it’s a long life pot designed to operate 10,000 times.

During normal use, the difference between the low…

…and the high position is about 75 degrees.

However, the pot actually moves a lot further.

A full 250 degrees.

So it really only uses about 1/3rd of its possible travel in normal use. It’s a sort of a problem but nothing major.

What Is A Potentiometer?

It’s a variable resistor that has 3 connections. The outside connections are joined by a resistive strip. The central connection moves along the resistive strip to increase or decrease the distance that the power has to travel through the resistive strip. The further it has to travel, the higher the resistance.


Since the smart only uses a small section of the potentiometer, it’s more prone to wear and corrosion. Anything that affects the resistance output will confuse the heater controller.


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